The pelletizing process is a compression or molding of a material in the form of pellets. A variety of different materials can undergo such a process, including chemicals, iron ore, animal feed, and the like. In the case of iron ore pellets, ultrafine particles are obtained by means of a heat treatment. An ultrafine fraction (below 0.15 mm) is thus found in nature or generated in the processing. The pellet can be formed in spherical clusters of various sizes ranging from 8 to 18 mm, with features suitable for feeding of reduction units, such as blast furnaces.
In all pelletizing processes of iron ores used industrially, there is a step of thermal hardening of the pellets. One of the known processes applies a “Traveling Grate” type furnace. In this case, the burning of the material takes place in a bed of pellets placed on a metallic surface with a limited working temperature, in order to avoid damage to the equipment. These limits imply lower temperatures in the layers closer to the metal surfaces; such temperatures are not sufficient to ensure a complete sintering of the particles, which does not allow filling the entire volume of the burning equipment with green pellets. In these processes, a layer of recirculated burnt pellets is applied on the metal surfaces, side and bottom, in order to avoid the said problems.
The said traveling grate furnace process to produce burnt pellets of iron ore requires the recirculation of 20 to 30% by weight of the produced material to form the liner layer, side and bottom, in the metallic surfaces.
DE 4109396 describes a method of production of iron ore pellets, comprising recirculating cover elements which protect the metallic structure of the heating equipment.
So no teaching or knowledge of prior art discloses a process for pelletizing iron ores which brings a more innovative, efficient and economical solution for the metallic surfaces heating problem during the iron ore pellet's burning step, bringing inconvenience in the production thereof.